Threshold voltage adjustable field effect transistor biosensor using tri-layer electrodes

Abstract

A microelectronic structure for bio-sensing includes a field-effect-transistor having a channel layer. A first layer of SiO2 is arranged on the channel layer, and a second layer of HfO2 is arranged on top of the first layer. A tri-layer metal electrode is arranged on the top of the second layer, the tri-layer metal electrode includes a bottom layer, an alloy layer on top of the bottom layer, and a top layer. A third layer constructed of an oxide material is arranged on top of the tri-layer metal electrode. A thickness of the bottom layer or the alloy layer of the tri-layer metal electrode is based on a pH of a test solution.

What is claimed is: 
     
         1 . A microelectronic structure comprising:
 a field-effect-transistor (FET) including a channel layer;   a first layer comprising SiO 2  on the channel layer;   a second layer comprising HfO 2  on top of the first layer;   a tri-layer metal electrode on top of the second layer, the tri-layer metal electrode comprising a bottom layer, an alloy layer on top of the bottom layer of the tri-layer metal electrode, and a top layer; and   a third layer comprising an oxide material on top of the tri-layer metal electrode,   wherein a thickness of the bottom layer of the tri-layer metal electrode is based on a pH of a test solution.   
     
     
         2 . The microelectronic structure according to  claim 1 , wherein a threshold voltage (V t ) of the FET is set based on the thickness of the bottom layer of the tri-layer metal electrode. 
     
     
         3 . The microelectronic structure according to  claim 1 , wherein the thickness of the bottom layer is configured to increase based on an increase of the pH of the test solution. 
     
     
         4 . The microelectronic structure according to  claim 1 , wherein the thickness of the bottom layer of the tri-layer metal electrode is between 5 to 100 Angstroms. 
     
     
         5 . The microelectronic structure according to  claim 1 , wherein the alloy layer of the tri-layer metal electrode is an Al alloy selected from the group consisting of TiAl, TiAlC, TaAl, TaAlC, AlC, or Al. 
     
     
         6 . The microelectronic structure according to  claim 1 , wherein:
 the bottom layer of the tri-layer metal electrode comprises TiN;   the alloy layer of the tri-layer metal electrode comprises an Al alloy; and   the bottom layer of the tri-layer metal electrode comprises TiN.   
     
     
         7 . The microelectronic structure according to  claim 1 , wherein the oxide material of the third layer is selected from the group consisting of HfO 2 , SiO 2 , or Al 2 O 3 . 
     
     
         8 . The microelectronic structure according to  claim 7 , wherein the oxide material of the third layer includes a sensing surface exposed for contact with the test solution. 
     
     
         9 . The microelectronic structure according to  claim 8 , further comprising a reference electrode configured to charge the test solution in contact with the sensing surface of the oxide material of the third layer. 
     
     
         10 . A microelectronic structure comprising:
 a field-effect-transistor (FET) including a channel layer;   a first layer comprising SiO 2  on the channel layer;   a second layer comprising HfO 2  on top of the first layer;   a tri-layer metal electrode on top of the second layer, the tri-layer metal electrode comprising a bottom layer, an alloy layer on top of the bottom layer, and a top layer; and   a third layer comprising an oxide material on top of the tri-layer metal electrode,   wherein a thickness of the alloy layer of the tri-layer metal electrode is based on a pH of a test solution.   
     
     
         11 . The microelectronic structure according to  claim 10 , wherein a threshold voltage (V t ) of the FET is set based on the thickness of the alloy layer of the tri-layer metal electrode. 
     
     
         12 . The microelectronic structure according to  claim 10 , wherein the thickness of the alloy layer is configured to decrease based on an increase of the pH of the test solution. 
     
     
         13 . The microelectronic structure according to  claim 10 , wherein the thickness of the alloy layer of the tri-layer metal electrode is between 5 to 100 Angstroms. 
     
     
         14 . The microelectronic structure according to  claim 10 , wherein the alloy layer of the tri-layer metal electrode is an Al alloy selected from the group consisting of TiAl, TiAlC, TaAl, TaAlc, AiC, or Al. 
     
     
         15 . The microelectronic structure according to  claim 10 , wherein:
 the bottom layer of the tri-layer metal electrode comprises TiN;   the alloy layer of the tri-layer metal electrode comprises an Al alloy; and   the bottom layer of the tri-layer metal electrode comprises TiN.   
     
     
         16 . The microelectronic structure according to  claim 10 , wherein the oxide material of the third layer is selected from the group consisting of HfO 2 , SiO 2 , or Al 2 O 3 . 
     
     
         17 . The microelectronic structure according to  claim 16 , wherein the oxide material of the third layer includes a sensing surface exposed for contact with the test solution. 
     
     
         18 . The microelectronic structure according to  claim 17 , further comprising a reference electrode arranged to charge the test solution in contact with the sensing surface of the oxide material of the third layer. 
     
     
         19 . A method of manufacturing a microelectronic structure for bio-sensing, the method comprising:
 providing a field-effect-transistor (FET) including a channel layer;   arranging a first layer constructed of SiO 2  on the channel layer;   arranging a second layer constructed of HfO 2  on top of the first layer;   arranging a tri-layer metal electrode on top of the second layer, the tri-layer metal electrode includes a bottom layer, an alloy layer on top of the bottom layer, and a top layer; and   arranging a third layer comprising an oxide material on top of the tri-layer metal electrode;   wherein a thickness of the alloy layer or the bottom layer of the tri-layer metal electrode is based on a pH of a test solution.   
     
     
         20 . The method according to  claim 19 , further comprising setting a threshold voltage (V t ) of the FET based on the thickness of the bottom layer or the alloy layer of the tri-layer metal electrode.